U.S. patent application number 13/526951 was filed with the patent office on 2012-10-11 for heart valve prosthesis and methods of manufacture and use.
This patent application is currently assigned to Medtronic Corevalve, Inc.. Invention is credited to Stanley Komatsu, Robrecht Michiels, Hung Nguyen, Mykim Nguyen, Than Nguyen.
Application Number | 20120259409 13/526951 |
Document ID | / |
Family ID | 37420182 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120259409 |
Kind Code |
A1 |
Nguyen; Than ; et
al. |
October 11, 2012 |
Heart Valve Prosthesis and Methods of Manufacture and Use
Abstract
A heart valve prosthesis is provided having a self-expanding
multi-level frame that supports a valve body comprising a skirt and
plurality of coapting leaflets. The frame transitions between a
contracted delivery configuration that enables percutaneous
transluminal delivery, and an expanded deployed configuration
having an asymmetric hourglass shape. The valve body skirt and
leaflets are constructed so that the center of coaptation may be
selected to reduce horizontal forces applied to the commissures of
the valve, and to efficiently distribute and transmit forces along
the leaflets and to the frame. Alternatively, the valve body may be
used as a surgically implantable replacement valve prosthesis.
Inventors: |
Nguyen; Than; (Placentia,
CA) ; Nguyen; Hung; (Garden Grove, CA) ;
Nguyen; Mykim; (Santa Ana, CA) ; Komatsu;
Stanley; (Laguna Hills, CA) ; Michiels; Robrecht;
(Laguna Hills, CA) |
Assignee: |
Medtronic Corevalve, Inc.
Minnapolis
MN
|
Family ID: |
37420182 |
Appl. No.: |
13/526951 |
Filed: |
June 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13075194 |
Mar 30, 2011 |
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13526951 |
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11128826 |
May 13, 2005 |
7914569 |
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13075194 |
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Current U.S.
Class: |
623/2.15 ;
623/2.19 |
Current CPC
Class: |
A61F 2/2415 20130101;
A61F 2220/005 20130101; A61F 2230/0067 20130101; A61F 2/2418
20130101; A61F 2220/0075 20130101; A61F 2230/008 20130101; A61F
2220/0058 20130101; Y10S 623/90 20130101; A61F 2230/0054 20130101;
A61F 2/2412 20130101; A61F 2250/0039 20130101 |
Class at
Publication: |
623/2.15 ;
623/2.19 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Claims
1-22. (canceled)
23: A valve prosthesis comprising: a valve body comprising three
leaflets, wherein adjoining leaflets are sewn together to form
commissures; and a self-expanding frame, the frame having an inflow
section having a first row of cells, an outflow section having a
second row of cells and including an eyelet, and a middle region
between the inflow section and the outflow section, wherein the
middle region is configured to avoid blocking blood flow to the
coronary arteries when the frame is implanted in a body, wherein
the area of individual cells in the first row of cells is less than
the area of individual cells in the second row of cells, wherein
the frame supports the valve body, wherein the frame has a
longitudinal axis, wherein the frame has a contracted delivery
configuration and an expanded deployed configuration, wherein, when
the frame is in the expanded deployed configuration, the outflow
section has a larger diameter than the inflow section, wherein a
plurality of cells of the frame are positioned between the cells
spanned by commissures, wherein each leaflet has a free edge that
is suspended from the leaflet's commissures to define coaptation
edges and a center of coaptation, and wherein the length of each
free edge forms a substantially continuous curve extending
downwardly between the respective commissures so that the free
edges of the leaflets generally define the shape of catenaries to
substantially uniformly distribute loads over the leaflets.
24: The valve prosthesis of claim 23, wherein the leaflets comprise
porcine, bovine, equine or other mammalian pericardial tissue,
synthetic material, or polymeric material.
25: The valve prosthesis of claim 23, wherein the leaflets are sewn
to a skirt at joints, wherein the skirt is sewn to the inflow
section of the frame, and wherein the joints are affixed to the
frame to evenly distribute forces through the valve body to the
frame.
26: The valve prosthesis of claim 25, wherein the frame further
comprises a cell pattern that defines a contour configured to
support the joints.
27: The valve prosthesis of claim 23, wherein the frame comprises a
cell pattern defined by unequal length zig-zags.
28: The valve prosthesis of claim 23, wherein the commissures are
affixed to the frame at a location proximal of the center of
coaptation.
29: The valve prosthesis of claim 23, wherein the commissures
include flaps that span an entire area a cell.
30: The valve prosthesis of claim 23, wherein the frame is
configured to permit access to a patient's coronary arteries in the
expanded deployed configuration.
31: The valve prosthesis of claim 23, wherein at least one cell in
the outflow section is larger than at least one cell in the inflow
section.
32: The valve prosthesis of claim 23, wherein a cell in the outflow
section has a first area, wherein a cell in the inflow section has
a second area, and wherein the first area is larger than the second
area.
33: The valve prosthesis of claim 23, wherein the inflow section
includes a first row of cells, wherein the outflow section includes
a second row of cells, and wherein the number of cells in the first
row of cells is equal to the number of cells in the second row of
cells.
34: The valve prosthesis of claim 23, wherein the middle region and
the outflow section comprise a cell pattern that provides a
pre-determined radius of curvature for a transition from the middle
region to the outflow section when the frame is in the expanded
deployed configuration.
35: The valve prosthesis of claim 23, wherein the diameter of the
constriction region is less than the diameter of the inflow
section.
36: The valve prosthesis of claim 23, wherein the outflow section
includes exactly three eyelets.
37: The valve prosthesis of claim 23, wherein the frame includes
four rows of cells.
38: A valve prosthesis comprising: a valve body comprising three
leaflets, wherein adjoining leaflets are sewn together to form
commissures; and a self-expanding frame comprising a plurality of
cells, the frame having an inflow section, an outflow section, and
a middle region between the inflow section and the outflow section,
wherein the middle region is configured to avoid blocking blood
flow to the coronary arteries when the frame is implanted in a
body, wherein the frame supports the valve body, wherein the frame
has a longitudinal axis, wherein the frame has a contracted
delivery configuration and an expanded deployed configuration,
wherein, when the frame is in the expanded deployed configuration,
the outflow section has a larger diameter than the inflow section,
wherein each commissure is configured to span a cell of the frame
to distribute force within the commissures and to the frame, and
wherein a plurality of cells of the frame are positioned between
the cells spanned by commissures, wherein each leaflet has a free
edge that is suspended from the leaflet's commissures to define
coaptation edges and a center of coaptation, and wherein the length
of each free edge forms a substantially continuous curve extending
downwardly between the respective commissures so that the free
edges of the leaflets generally define the shape of catenaries to
substantially uniformly distribute loads over the leaflets.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to replacement valves for
improving the cardiac function of a patient suffering from cardiac
valve dysfunction, such as aortic valve regurgitation or aortic
stenosis. More particularly, the present invention relates to heart
valve prostheses that provide improved durability and are
particularly well-suited for percutaneous delivery.
[0003] 2. Background of the Invention
[0004] Heart valve replacement has become a routine surgical
procedure for patients suffering from valve regurgitation or
stenotic calcification of the leaflets. While certain procedures
may be performed using minimally-invasive techniques (so-called
"keyhole" techniques), the vast majority of valve replacements
entail full sternotomy and placing the patient on cardiopulmonary
bypass. Traditional open surgery inflicts significant patient
trauma and discomfort, requires extensive recuperation times and
may result in life-threatening complications.
[0005] To address these concerns, within the last decade efforts
have been made to perform cardiac valve replacements using
minimally-invasive techniques. In these methods, laparascopic
instruments are employed to make small openings through the
patient's ribs to provide access to the heart. While considerable
effort has been devoted to such techniques, widespread acceptance
has been limited by the clinician's ability to access only certain
regions of the heart using laparoscopic instruments.
[0006] Still other efforts have been focused on percutaneous
transluminal delivery of replacement cardiac valves to solve the
problems presented by traditional open surgery and
minimally-invasive surgical methods. In such methods; a valve
prosthesis is compacted for delivery in a catheter and then
advanced, for example, through an opening in the femoral artery and
through the descending aorta to the heart, where the prosthesis
then is deployed in the aortic valve annulus. Although transluminal
techniques have attained widespread acceptance with respect to
delivery of stents to restore vessel patency, only mixed results
have been obtained with respect to percutaneous delivery of
relatively more complicated valve prostheses.
[0007] One such example of a previously-known device heart valve
prosthesis is described in U.S. Pat. No. 6,454,799 to Schreck. The
prosthesis described in that patent comprises a fabric-based heart
valve disposed within a plastically deformable wire-mesh base, and
is delivered via expansion of a balloon catheter. One drawback with
balloon catheter delivery of the prosthetic valve is that the valve
leaflets may be damaged when compressed between the balloon and the
base during deployment. In addition, because balloon expandable
structures tend to experience some recoil following balloon
deflation, perivalvular leaks may develop around the circumference
of the valve prosthesis.
[0008] Accordingly it would be desirable to provide a
percutaneously-deliverable valve prosthesis that reduces the risk
of leaflet damage during deployment of the prosthesis. It further
would be. desirable to provide a valve prosthesis that reduces the
risk of perivalvular leaks resulting from recoil of the prosthesis
following deployment.
[0009] U.S. Pat. No. 6,027,525 to Suh, et al. describes a valve
prosthesis comprising a series of self-expanding units affixed to a
polymeric cover and having a valve disposed therein. Such devices
are not suitable for cardiac valve replacement because of the
limited ability to compact the valve disposed within the
prosthesis. Moreover, such valve prostheses would be particularly
undesirable for treating aortic valve defects, because the
polymeric cover would obscure the ostia of the coronary arteries,
both disrupting blood flow to the coronary arteries and preventing
subsequent catheterization of those arteries. Accordingly, it would
be desirable to provide a valve prosthesis that is self-expanding,
yet permits the valve to be compacted to a greater degree than
previously-known designs.
[0010] U.S. Pat. No. 6,682,559 to Myers, et al. also describes a
valve prosthesis having an essentially tubular design. One drawback
of such configurations is that relatively large horizontal forces
arise along the coaptation edges of the leaflets and are
transmitted to the commissural points. These forces may adversely
affect the durability of the leaflets and lead to valve failure. In
view of this, it would be desirable to provide a valve wherein the
center of coaptation of the leaflets may be selected so as to
reduce horizontal forces applied to coaptation edges of the
leaflets and commissural points, thereby improving durability of
the valve. In addition, it would be desirable to provide a valve
design that more uniformly distributes horizontal forces over the
coaptation edges of the leaflets, rather than concentrating those
forces at the commissural points.
[0011] In an effort to more nearly recreate the force distribution
along the leaflets of natural tissue valves, some previously-known
valve designs include circular base portions having longitudinal
projections that function as anchors for the commissural points,
such as described in U.S. Pat. No. 5,855,601 to Bessler, et al. and
U.S. Pat. No. 6,582,462 to Andersen, et al.
[0012] While the valve prostheses of Bessler and Andersen may be
readily collapsed for delivery, those designs are susceptible to
problems once deployed. For example, the longitudinal projections
of such prostheses may not provide sufficient rigidity to withstand
compressive forces applied during normal movements of the heart.
Deformation of the commissural anchors may result in varied forces
being imposed on the commissures and leaflets, in turn adversely
impact functioning of the leaflets. In addition, because the
exteriors of the foregoing valve prostheses are substantially
cylindrical, the prostheses are less likely to adequately conform
to, and become anchored within the valve annulus anatomy during
deployment. As a result, cyclic loading of the valve may result in
some slippage or migration of the anchor relative to the patient's
anatomy.
[0013] In view of the foregoing, it would be desirable to provide a
valve that is capable of conforming to a patient's anatomy while
providing a uniform degree of rigidity and protection for critical
valve components. It therefore would be desirable to provide a
valve prosthesis having portions that are capable of deforming
circumferentially to adapt to the shape of the pre-existing valve
annulus, but which is not susceptible to deformation or migration
due to normal movement of the heart. Still further, it would be
desirable to provide a valve prosthesis having a multi-level
component that is anatomically shaped when deployed, thereby
enhancing anchoring of the valve and reducing the risk of migration
and perivalvular leaks.
BRIEF SUMMARY OF THE INVENTION
[0014] In view of the foregoing, it is an object of the present
invention to provide a valve prosthesis that overcomes the
drawbacks of previously-known designs, and which may be implanted
using open surgical, minimally invasive or percutaneous
implantation techniques.
[0015] It is also an object of the present invention to provide a
percutaneously-deliverable valve prosthesis that reduces the risk
of leaflet damage during deployment of the prosthesis.
[0016] It is a further object of this invention to provide a valve
prosthesis that reduces the risk of perivalvular leaks resulting
from elastic recoil of the prosthesis following deployment.
[0017] It is another object of the present invention to provide a
valve prosthesis that is self-expanding, yet permits the valve to
be compacted to a greater degree than previously-known designs and
permits ready access to adjoining anatomical structures, such as
the coronary arteries.
[0018] It is a still further object of the present invention to
provide a valve in which the center of coaptation of the leaflets
may be selected so as to reduce horizontal forces applied to
coaptation edges of the leaflets and commissural points, thereby
improving durability of the valve.
[0019] In addition, it is an object of this invention to provide a
valve design that more uniformly distributes forces over the
coaptation edges of the leaflets, rather than concentrating those
forces at the commissural points.
[0020] It is yet another object of this invention to provide a
valve that is anatomically shaped, provides a uniform high degree
of rigidity and protection for critical valve components, and which
is less susceptible to deformation arising from normal movement of
the heart.
[0021] It is an object of the present invention to provide a valve
prosthesis having portions that are capable of deforming
circumferentially to adapt to the shape of the pre-existing valve
annulus, but which is not susceptible to deformation or migration
due to normal movement of the heart.
[0022] It is also an object of this invention to provide a valve
prosthesis having a multi-level component that is anatomically
shaped when deployed, thereby enhancing anchoring of the valve and
reducing the risk of migration and perivalvular leaks.
[0023] It is a further object of the present invention to provide a
valve prosthesis wherein a valve is disposed within a rigid portion
of a multilevel frame, so that valve area and function are not
impaired, but inflow and/or outflow portions of the multilevel
frame are capable of conforming to patient anatomy anomalies.
[0024] It is a further object of the present invention to provide a
valve prosthesis that facilitates alignment of the heart valve
prosthesis with the direction of blood flow.
[0025] These and other objects of the present invention are
accomplished by providing a heart valve prosthesis wherein a
self-expanding multi-level frame supports a valve body comprising a
skirt and plurality of coapting leaflets. The frame has a
contracted delivery configuration, in which the prosthesis may be
stored within a catheter for percutaneous delivery, and an expanded
deployed configuration having an asymmetric hourglass shape. The
valve body skirt and leaflets preferably are constructed of
porcine, bovine, equine or other mammalian tissue, such as
pericardial tissue, and are sewn, welded, molded or glued together
so as to efficiently distribute forces along the leaflets and to
the frame. Alternatively, the valve body may comprise a synthetic
or polymeric material.
[0026] In accordance with the principles of the present invention,
the frame comprises multiple levels, including a proximal conical
inflow section, a constriction region and a flared distal outflow
section. Each of the inflow and outflow sections is capable of
deforming to a non-circular cross-section to conform to the
patient's anatomy, while the constriction region is configured to
retain a circular cross-section that preserves proper functioning
of the valve body.
[0027] The frame comprises a plurality of cells having a pattern
that varies along the length of the frame to provide a high degree
of anchoring and alignment of the valve prosthesis. The cell
pattern further is selected to provide a uniform diameter where the
commissural joints of the leaflets are attached to the frame, while
permitting the inflow and outflow regions to expand to conform to
the patient's anatomy. In this manner, optimal functioning of the
valve body may be obtained even though the frame may be deployed in
anatomies having a range of sizes. In addition, the frame resists
deformation caused by movement of the heart and enables a
functional portion of the valve body to be disposed supra-annularly
to the native valve, with a portion of the valve prosthesis
extending into the native valve annulus.
[0028] In one embodiment suitable for aortic valve replacement, the
valve body comprises a skirt coupled to three leaflets. Each of the
components preferably is formed of animal pericardial tissue or
synthetic material, and then sewn, glued, welded or molded
together. The lateral ends of the leaflets include enlarged regions
that are folded to both form the commissural joints and fasten the
commissural joints to the frame. The skirt and leaflets further are
configured so that the joints align with contours of the cell
pattern of the frame.
[0029] In a preferred embodiment, the commissural joints are
affixed to the frame at locations above the area of coaptation, to
provide a selectable center of coaptation of the leaflets. This
design provides a more efficient delivery configuration because the
commissures are not compressed against the leaflets when the valve
prosthesis is reduced to the contracted delivery configuration.
Additionally, by lengthening the distance to the commissures, the
design mimics the functioning of natural tissue valves by
distributing forces along the coaptation edges and reducing
horizontal forces transmitted to the commissural joints.
[0030] In alternative embodiments, the valve body of the present
invention may include a sewing ring in lieu of the frame to
facilitate surgical implantation, and may employ as few as two and
as many as four leaflets.
[0031] Methods of making and using the valve prostheses of the
present invention are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0032] The above and other objects and advantages of the present
invention will be apparent upon consideration of the following
detailed description, taken in conjunction with the accompanying
drawings, in which like reference numerals refer to like parts
throughout, and in which:
[0033] FIGS. 1A, 1B and 1C are, respectively, side and top end
views of an exemplary valve prosthesis of the present invention in
the expanded deployed configuration and an enlarged region of the
frame of the valve prosthesis;
[0034] FIG. 2 is a side view of the frame of the valve prosthesis
of FIGS. 1 in a contracted delivery configuration;
[0035] FIGS. 3A and 3B are, respectively, plan views of a leaflet
and the skirt employed in the valve body of the present
invention;
[0036] FIGS. 4A and 4B are, respectively, a perspective view of a
leaflet with its enlarged regions folded, and a plan view of the
valve body of the present invention, wherein the leaflets are
fastened to the skirt;
[0037] FIG. 5 is a side view of the valve body of FIG. 4B fully
assembled; and
[0038] FIG. 6 is a side view depicting the valve prosthesis of the
present invention deployed atop a patient's aortic valve.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The present invention is directed to a heart valve prothesis
having a self-expanding frame that supports a valve body. In a
preferred embodiment, the frame has a tri-level asymmetric
hourglass shape with a conical proximal section, an enlarged distal
section and a constriction region having a predefined curvature
when the frame is deployed. In the context of the present
application, the proximal section constitutes the "inflow" portion
of the valve prosthesis and is disposed in the aortic annulus of
the patient's left ventricle, while the distal section constitutes
the "outflow" portion of the valve prosthesis and is positioned in
the patient's ascending aorta.
[0040] In a preferred embodiment the valve body comprises three
leaflets that are fastened together at enlarged lateral end regions
to form commissural joints, with the unattached edges forming the
coaptation edges of the valve. The leaflets are fastened to a
skirt, which is in turn affixed to the frame. The enlarged lateral
end regions of the leaflets permit the material to be folded over
to enhance durability of the valve and reduce stress concentration
points that could lead to fatigue or tearing of the leaflets. The
commissural joints are mounted above the plane of the coaptation
edges of the valve body to minimize the contracted delivery profile
of the valve prosthesis, while the configuration of the edges
permits uniform stress distribution along the coaptation edges.
[0041] Referring to FIGS. 1, an exemplary embodiment of a valve
prosthesis constructed in accordance with the principles of the
present invention is described. Valve prosthesis 10 comprises
expandable frame 12 having valve body 14 affixed to its interior
surface, e.g., by sutures. Frame 12 preferably comprises a
self-expanding structure formed by laser cutting or etching a metal
alloy tube comprising, for example, stainless steel or a shape
memory material such as nickel titanium. The frame has an expanded
deployed configuration which is impressed upon the metal alloy tube
using techniques that are per se known in the art. Valve body 14
preferably comprises individual leaflets assembled to a skirt,
where all of the components are formed from a natural or man-made
material. Preferred materials for valve body 14 include mammalian
tissue, such as porcine, equine or bovine pericardium, or a
synthetic or polymeric material.
[0042] Frame 12 preferable includes multiple levels, including
outflow section 15, inflow section 16 and constriction region 17.
As depicted in the enlarged view of FIG. 1B, the frame comprises a
plurality of cells having sizes that vary along the length of the
prosthesis. As indicated by dotted lines a, band c, each cell
comprises two zig-zag structures having unequal-length struts,
wherein the vertices of the zig-zags are coupled together. For
example, zig-zag 18 has length z.sub.1 whereas zig-zag 19 has
greater length Z.sub.2. This cell design permits each level of
cells between the proximal and distal ends of the frame to be
tailored to meet specific design requirements, such as,
compressibility, expansion characteristics, radial strength and so
as to define a suitable contour for attachment of the valve
body.
[0043] The cell pattern of frame 12 also enables the frame to
expand to the tri-level asymmetric hourglass shape depicted in FIG.
IA, having conical inflow section, enlarged outflow section and
fixed diameter constricted region. Each section of frame 12 has a
substantially circular cross-section in the expanded deployed
configuration, but in addition the cell patterns of the inflow and
outflow sections permit those sections to adapt to the specific
anatomy of the patient, thereby reducing the risk of migration and
reducing the risk of perivalvular leaks. The cell patterns employed
in the constriction region are selected to provide a uniform
circular cross-section area for the constriction region when
deployed, and a pre-determined radius of curvature for the
transition between the constriction region and outflow section of
the frame. In particular, the convex-concave shape of frame 12
within the constriction region ensures that the frame is held away
from the opposing sinus wall in the ascending aorta, thus ensuring
adequate blood flow to the coronary arteries and facilitating
catheter access to the coronary arteries.
[0044] Enlarged outflow section has nominal deployed diameter
D.sub.o, inflow section has nominal deployed diameter D.sub.I, and
constriction region has deployed substantially fixed diameter
D.sub.c. The conical shape of the inflow region and smooth
transitions between adjacent sections of frame 12 are expected to
be particularly advantageous in directing blood flow through the
valve body with little or no turbulence, as compared to step
changes in diameter observed for surgically implanted replacement
valves.
[0045] The above-described cell pattern permits each of the inflow
and outflow sections of frame 12 to expand to a diameter within a
range of deployed diameters, while retaining constriction region 17
at a substantially constant diameter. Thus, for example, outflow
diameter D.sub.o may range from 30 to 55 mm, while inflow diameter
D.sub.I may vary from 19 to 34 mm. Illustratively, frame 12 may be
manufactured in four sizes having a range of diameters D.sub.o,
D.sub.I and D.sub.c as set forth in Table 1 below:
TABLE-US-00001 TABLE 1 Size A Size B Size C Size D D.sub.o 40 mm 50
mm 40 mm 50 mm D.sub.c 22 mm 22 mm 24 mm 24 mm D.sub.l 26 mm 26 mm
29 mm 29 mm
[0046] Advantageously, these four frame sizes are expected to cover
a wide range of patient anatomies, while requiring construction of
only two sizes of valve bodies (22 and 24 mm). Compared to
previously-known commercially available surgical valves, which vary
from approximately 17 mm to 31 mm in one millimeter increments, it
is expected that the above four sizes of valve prosthesis of the
present invention could be used for more than 75% of the patient
population, thus greatly 20 reducing the costs associated with
manufacturing and inventorying large numbers of parts.
[0047] When configured as a replacement for an aortic valve, inflow
section 16 extends into and anchors within the aortic annulus of a
patient's left ventricle and 25 outflow section 15 is positioned in
the patient's ascending aorta. Importantly, the configuration of
outflow section 15 is expected to provide optimal alignment of the
valve body with the direction of blood flow. In addition, the cell
pattern of outflow section 15 also serves to anchor the outflow
section in the patient's ascending aorta to prevent lateral
movement or migration of frame 12. As depicted in FIG. 1C, the use
of relatively larger cells in the outflow section of frame 12,
combined with the convex-concave shape of constriction region 17,
ensures that the frame does not obstruct blood flow to the
patient's coronary arteries when deployed and allows for catheter
access to the coronary arteries. Frame 12 also may include eyelets
20 for use in loading the heart valve prosthesis 10 into a delivery
catheter.
[0048] Still referring to FIGS. 1, valve body 14 includes skirt 21
affixed to frame 12, and leaflets 22. Leaflets 22 are attached
along their bases to skirt 21, for example, using sutures 23 or a
suitable biocompatible adhesive. Adjoining pairs of leaflets are
attached to one another at their lateral ends to form commissures
24, with free edges 25 of the leaflets forming coaptation edges
that meet in area of coaptation 26.
[0049] As depicted in FIG. 1A, the curve formed at joint 27 between
the base of each leaflet 22 and skirt 21 follows the contour of the
cell pattern of frame 12, so that most of the length of joint 27 is
directly supported by frame 12, thereby transmitting forces applied
to the valve body directly to the frame. As further depicted in
FIG. 1C, commissures 24 are configured to span a cell of frame 12,
so that force is evenly distributed within the commissures and to
frame 12.
[0050] Referring to FIG. 2, valve prosthesis 10 is shown in the
contracted delivery configuration. In this state, valve prosthesis
may be loaded into a catheter for percutaneous transluminal
delivery via a femoral artery and the descending aorta to a
patient's aortic valve. In accordance with one aspect of the
present invention, commissures 24 are disposed longitudinally
offset from coaptation edges 25 of the valve body, thereby
permitting a smaller delivery profile than achievable with
previously-known replacement valves. In addition, because frame 12
self-expands upon being released from the delivery catheter, there
is no need to use a balloon catheter during placement of valve
prosthesis 10, thereby avoiding the potential for inflicting
compressive injury to the valve leaflets during inflation of the
balloon.
[0051] Referring now to FIGS. 3A and 3B, skirt 21 and leaflet 22 of
a preferred aortic valve embodiment of the present invention are
described. Skirt 21 and leaflet 22 preferably are cut from a sheet
of animal pericardial tissue, such as porcine pericardial tissue,
or synthetic or polymeric material, either manually or using a die
or laser cutting system. The pericardial tissue may be processed in
accordance with tissue processing techniques that are per se known
in the art for forming and treating tissue valve material.
Alternatively, skirt 21 and leaflet 22 may be constructed on a
synthetic or polymeric material. In a preferred embodiment, skirt
21 and leaflets 22 have a thickness of between 0.008'' and 0.016'',
and more preferably between 0.012'' and 0.014''.
[0052] Leaflet 22 includes enlarged lateral ends 30 and 31 disposed
at either end of free edge 32, and body 33. Free edge 32 forms
coaptation edge 25 of the finished valve body 14, while lateral
ends 30 and 31 are folded and joined to adjacent leaflets to form
commissures 24. In accordance with one aspect of the present
invention, free edges 32 assume the form of catenaries when the
valve body is affixed to frame 12, thereby providing uniform
loading along the length of the coaptation edge in a manner similar
to a suspension bridge. Body 33 is joined to skirt 21 as described
below. Lateral ends 30 and 31 illustratively are shown in FIG. 3A
as having fold lines d, e and f, to define flaps 34, 35 and 36.
[0053] Skirt 21 preferably is constructed from the same material as
leaflets 22, and includes scalloped areas 37, reinforcing tabs 38
and end tabs 39. Each scalloped area 37 is joined to a body 33 of a
respective leaflet 22. Reinforcing tabs 38 illustratively include
fold lines g, h and i, except for reinforcing tabs 40 and 41 at the
lateral ends of the skirt, which have only one fold apiece. As
described below, reinforcing tabs 40 and 41 are joined to one
another, e.g., by sutures or gluing, so that skirt 21 forms a
frustum of a cone.
[0054] End tabs 39 are folded over the ends of the proximal-most
row of cells of frame 12 to secure skirt 21 to the frame and seal
against perivalvular bypass flows (see FIG. 1A). Because end tabs
39 are directly supported by the last zig-zag row of cells of frame
12, there is no opportunity for an unsupported edge of the skirt to
flap or otherwise extend into the flow path along the inflow edge
of skirt 21. Thus, the design of the valve prosthesis not only
ensures that there are no flaps to disrupt flow or serve as sites
for thrombus formation, but also reduces the risk that hemodynamic
flow against such flaps could cause frame 12 to migrate.
[0055] Referring to FIGS. 4A and 4B, assembly of valve body 14 from
skirt 21 and leaflets 22 is described. In FIG. 4A, flap 34 first is
folded along line d. Flap 35 is folded along line e so that it lies
atop flap 34, forming seam 42 comprising a triple thickness of the
tissue. Flap 36 then is folded along line f. Adjoining leaflets 22
then are fastened together along adjacent seams 42, resulting in a
leaflet assembly.
[0056] Reinforcing tabs 38 are folded along lines g, h and i to
form seams 43 comprising a double thickness of tissue. Next, the
leaflet assembly is attached to skirt 21 along the bottom edges of
bodies 33 of the leaflets to form joints 44. At this stage of the
assembly, prior to attaching reinforcing tab 40 to 41 and the
remaining seam 43 of leaflets 22, the valve body appears as
depicted in FIG. 4B. Reinforcing tabs 40 and 41 then are fastened
together to form another seam 43 along skirt 21 and the remaining
seam 43 between leaflets 22. Valve body 14 then is ready to be
affixed to frame 12.
[0057] Referring to FIG. 5, valve body 14 is shown as it would
appear when affixed to frame 12, but with frame 12 omitted to
better illustrate where the valve body is affixed to the frame.
During the step of affixing the valve body to the frame, flaps 36
of adjacent leaflets are affixed, e.g., by sutures, to span a cell
of the frame to support commissures 24 (compare to FIG. 1B) and end
tabs 39 are folded over and affixed to the proximal-most row of
cells of the frame 12 (compare to FIG. 1A). Valve body 14 also is
attached to frame 12 along seams 43 formed by the reinforcing tabs.
Each joint 44 is aligned with and fastened to (e.g., by sutures or
glue) to a curved contour defined by the struts of the cells of
frame 12, so that joint 44 is affixed to and supported by frame 12
over most of the length of the joint. As discussed above, the
configuration of the cells in frame 12 may be specifically
customized define a curved contour that supports joints 44 of the
valve body.
[0058] When completely assembled to frame 12, valve body 14 is
affixed to frame 12 along the edges of flaps 36 of the commissures,
end tabs 39, leaflet seams 42, reinforcing tab seams 43 and joints
44. In this manner, forces imposed on leaflets 22, commissures 24
and joints 44 are efficiently and evenly distributed over the valve
body and transferred to frame 12, thus reducing stress
concentration and fatigue of the valve body components. Moreover,
the use of multiple thicknesses of material along seams 42 and 43
is expected to provide a highly durable valve body which will last
for many years once implanted in a patient.
[0059] In accordance with another aspect of the present invention,
the center of coaptation of leaflets 22 is a distance L below the
point at which the commissures are affixed to the frame, as shown
in FIG. 5. Compared to previously-known designs, in the present
invention the overall lengths of the coaptation edges are
increased, while leaflets 22 coapt along a shorter portion of those
lengths. Several advantages arise from this design: [0060] the
leaflets require only minimal pressure to open and have a rapid
closing time. [0061] the valve demonstrates better washing dynamics
when open, i.e., less turbulence along the free edges of the
leaflets. [0062] the valve provides a more uniform distribution of
stresses along the coaptation edges of leaflets 22. [0063] the
angle at which force is transmitted to the commissures is
increased, thereby substantially reducing the horizontal forces
applied to the commissures that tend to pull the commissures away
from the frame. [0064] controlling the center of the height of
coaptation allows the commissures to be located proximal of the
center of coaptation, thereby reducing the contracted delivery
profile of the valve prosthesis.
[0065] All of the foregoing benefits are expected to reduce
non-uniform loads applied to -the-valve body, and substantially
enhance the durability of the valve prosthesis.
[0066] As will of course be apparent to one of skill in the art of
prosthetic valve design, the assembly steps described above are
merely illustrative, and a different order of assembling the
leaflets and skirt to form valve body 14 may be employed. In an
alternative embodiment, a conventional sewing ring may be attached
to valve body 14 and frame 12 may be omitted. In this case, the
valve prosthesis may be implanted surgically, rather than by
percutaneous transluminal delivery. In this case, commissures 24
may be attached to the ascending aorta by sutures or other means as
described above.
[0067] Referring now to FIG. 6, implantation of valve prosthesis 10
of the present invention is described. As discussed above, valve
prosthesis preferably comprises a self-expanding multilevel frame
that may be compressed to a contracted delivery configuration, as
depicted in FIG. 3, onto an inner member of a delivery catheter.
The valve prosthesis and inner member may then be loaded into a
delivery sheath of conventional design, e.g., having a diameter of
less than 20-24 French. Due in part to the fact that commissures 24
are longitudinally offset from the coaptation edges of the
leaflets, and also due to the ability to customize the cell pattern
along the length of the frame, it is expected that valve prosthesis
may be designed to achieve a significantly smaller delivery profile
than previously-known percutaneously-deliverable replacement
valves.
[0068] The delivery catheter and valve prosthesis are then advanced
in a retrograde manner through a cut-down to the femoral artery and
into the patient's descending aorta. The -catheter-then is
advanced, under fluoroscopic guidance, over the aortic arch,
through the ascending aorta and mid-way across the defective aortic
valve. Once positioning of the catheter is confirmed, the sheath of
the delivery catheter may be withdrawn proximally, thereby
permitting the valve prosthesis to self-expand.
[0069] As the valve prosthesis expands, it traps leaflets LN of the
patient's defective aortic valve against the valve annulus,
retaining the native valve in a permanently open state. As further
illustrated in FIG. 6, outflow section 15 of the valve prosthesis
expands against and aligns the prosthesis within the ascending
aorta, while inflow section 16 becomes anchored in the aortic
annulus of the left ventricle, so that skirt 21 reduces the risk of
perivalvular leaks.
[0070] As also seen in FIG. 6, the deployed configuration of
constriction region 17 holds valve body 14 in a superannular
position, away from the heart walls, thereby ensuring that the
constriction region expands to the predetermined fixed diameter.
This in turn ensures that the valve body does not experience any
unexpected lateral loads and therefore expands to its design
diameter, e.g., illustratively either 22 or 24 mm as in Table 1
above.
[0071] Because outflow section 15 of frame 12 employs relatively
larger cells than the remainder of the frame, valve prosthesis 10
does not disrupt blood flow into coronary arteries CA when
deployed, and also does not obstruct subsequent catheter access to
the coronary arteries. Accordingly, a clinician may readily gain
access to the coronary arteries, for example, to perform
angioplasty or stenting, simply by directing the angioplasty or
stent delivery system guide wire through the openings in the cell
pattern of frame 12.
[0072] While preferred embodiments of the invention are described
above, it will be apparent to one skilled in the art that various
changes and modifications may be made. The appended claims are
intended to cover all such changes and modifications that fall
within the true spirit and scope of the invention.
* * * * *